A man has been arrested at a government site where a controversial badger cull is expected to begin. The suspect was held at Aston Down in Stroud by Gloucestershire police.

He was detained on suspicion of aggravated trespass at the site belonging to the Department for Environment, Food and Rural Affairs (Defra).

Campaigners against the cull have said they are gearing up to protest against the "inhumane" measure. Activists from the Stop the Cull campaign group have already gathered in Gloucestershire, where one of two pilot schemes will take place, to form a "wounded badger patrol".

According to the group's website, the cull is expected to start on Tuesday and it is on "amber alert". Defra said authorised cull companies will decide when the badger cull will begin.

The culls are taking place in west Gloucestershire and west Somerset in a bid to combat the spread of bovine tuberculosis, which the National Farmers Union (NFU) said led to the slaughter of 38,000 cattle last year.

The cull was due to begin last autumn but was postponed while research continued into the population numbers in both areas. The government said west Somerset had approximately 4,300 badgers, while west Gloucesteshire's population was put at 3,600.

The cull aims to kill 70% of the animals, with west Somerset being set a minimum target of 2,081 and a maximum of 2,162. West Gloucestershire was set a minimum of 2,856 and a maximum of 2,932.

The culls, which will be carried out annually for four years, last six weeks and are allowed to take place between 1 June and 31 January.

If they are successful in stopping the spread of bovine TB, they could be rolled out further, saving millions in compensation to farmers.

Natural England, the public body responsible for the operation, did not release details of the two licence holders who will be conducting the culls.

Green party leader Natalie Bennett said: "I completely understand the distress that the continuing problem of TB in cattle is causing to farmers. But wanting to do something should not be pushing this government to make the terrible decision to go ahead with this cull, which could actually magnify the TB problem."

Shadow environment secretary Mary Creagh said via Twitter that the cull was "bad for farmers, bad for taxpayers and bad for wildlife".

A Defra spokesman said: "Bovine TB is spreading across England and devastating our cattle and dairy industries. In TB hotspots such as Gloucestershire and Somerset we need to deal with the infection in badgers if we're to get a grip on TB there. No country has dealt with the disease without tackling infection in both wildlife and cattle.

"We are working on new cattle and oral badger vaccines but they are years away from being ready and we cannot wait while this terrible disease spreads."

On Thursday a judge made an order to stop farmers involved in badger culls being harassed and abused, prompting a protester to say demonstrators would still aim to make the lives of farmers involved in badger culls a "misery".

Mr Justice Turner granted an injunction at a high court hearing in London after lawyers representing the National Farmers Union said farmers had been targeted.

The order includes provisions preventing protesters from entering private land without consent and protects farmers from threats and harassment – and anyone found to be in breach could face contempt of court proceedings.

Activist Jay Tiernan, who was named in court as a representative of the Coalition of Badger Action Groups, said he did not condone unlawful harassment.

But he said the injunction would not stop protests.

"It will make absolutely no difference whatsoever," he said after the hearing.

"We certainly do want to reduce the numbers of farmers involved. We like to think of ourselves as being very, very annoying."

He added: "We will use every available piece of legislation we can to make their lives a misery."

NFU president Peter Kendall welcomed the decision.

He said: "For beef and dairy farmers dealing with TB on their farms, these badger culls are an essential part in the fight against this terrible disease.

"Opinion is divided, so, while we recognise that not everyone agrees with the government's TB eradication policy, and the need to cull badgers to start to reduce this disease in cattle, we do acknowledge their legitimate right to hold peaceful protests.

"What we cannot condone are the actions being used by extreme activists designed to harass, intimidate and threaten others."